In recent years cell-based therapy of degenerative diseases has proven to be an interesting and potent therapeutic method for treating neurodegenerative diseases of the central nervous system (CNS), chronic liver diseases, heart diseases, arthritis or also tumors, among other things. Cell-based therapy is based on the replacement of injured cells, damaged cells, and/or cells which are impaired or degenerated in terms of their ability to regenerate and/or their normal activity with transplanted cells, which are either natural, i.e., non-modified, native cells or genetically modified cells. The replacement of these degenerated cells with native or genetically modified cells can be supported by, for example, trophic factors. As already mentioned, in the cell therapy method new cells are introduced into a diseased or degenerated tissue in order to regenerate the tissue that is diseased because of degenerated or no longer functional cells and thereby treat specific diseases. The cells presently used in the course of cell therapy are in particular stem cells or stem cell precursor cells, which are either autologous, i.e., obtained from the patient who is to be treated, or allogeneic, i.e., cells that were obtained from a donor. As a rule the stem cells or stem cell precursor cells differentiate in the tissue into which they are introduced into the cells that were originally present in the tissue, and do so under the influence of the surrounding tissue itself. Alternatively, at the present time use is also made of mature functional cells or genetically modified cells, which as a rule have been genetically modified to produce a specific substance that is either needed or lacking in the tissue in question.
Especially when stem cells are used, it is desirable to select the stem cells that are particularly active or possess an elevated potential to differentiate into the mature cells of the tissue into which said stem cells are introduced.
The mesenchymal stem cells presently used are multipotent adult stem cells and possess immunomodulatory properties, and are able to proliferate rapidly. They can therefore be used for a wide range of treatments, including for immunomodulatory therapy, for bone and cartilage regeneration, for myocardial regeneration, as well as for neurological or musculoskeletal diseases. To this end, the mesenchymal stem cells can either be introduced prior to their differentiation into the tissue in question, or they can be induced to differentiate in vitro into the desired cells in question and then introduced into the injured or degenerated tissue once they have differentiated. The cells, i.e., either the differentiated cells or the mesenchymal stem cells, then integrate themselves at the degeneration site and either replace the injured or degenerated tissue or counteract a progression of the injury/degeneration through their trophic and immunomodulatory activity, thereby partially or completely restoring the function of the organ or tissue.
As already mentioned above, for the regeneration of degenerated tissue in the course of cell therapy use can also be made of cells that act in an immunomodulatory manner in order to secrete soluble factors such as cytokines, chemokines, or growth factors, which express their efficacy in the vicinity of the introduced cells.
Therapy with adult stem cells represents an important milestone, particularly in the field of treating CNS diseases. In this case the therapeutic goal is to counteract the decline, i.e., the degeneration, of neurons by targeted protection or by new formation.
Accordingly, cell-based therapy has since been employed in nearly all kinds of neurodegenerative diseases (see for example Lee et al., Stem Cells 28: 329-343; Wang et al., 2006, Journal of Medical Investigation 53: 61-69) as well as in numerous acute CNS diseases such as traumatic brain injury, strokes, and also in tumor diseases.
In spite of the therapeutic effects of stem cells that have been demonstrated in preclinical studies, there are numerous problems associated with the cell implant techniques: when implanting stem cells there is often the risk that the transplanted cells will not achieve and maintain the desired phenotype, or that the transplanted cells will not survive in a stable therapeutic concentration in the central nervous system, or that an immune reaction will be triggered in the recipient tissue. Moreover, there is also the risk of the transplanted cells migrating from the transplant site and thus failing to bring about a regeneration of the degenerated tissue.
Against this background, it would be desirable to be able to select a subpopulation from the respective stem cell type and development stage, and to be able to evaluate this subpopulation for the cell-based therapy of degenerative diseases in terms of whether it possesses a better efficacy and safety profile than non-selected populations. Such a selection would be desirable for animal experiments as well as for the treatment of animals and humans, and consequently mammals in general.
Accordingly, the problem addressed by the present invention is that of providing a novel means with which cells that can be used successfully in cell therapy can be selected, or of providing such cells in general.